Along with the spread of data communication via network such as the Internet or a LAN, home networking which achieves inter-device communication by connecting home electrical appliances, computers, and other peripheral apparatuses through a network has been widely used in homes. The home networking enables content transmission and reception between apparatuses connecting to the network, and provides users with convenience and comfort.
Furthermore, to connect apparatuses one another, networking apparatuses which include a function that enables connection through wireless communication is expected to become increasingly widespread in the future, from a view point that networking apparatuses have high installation flexibility and can eliminate wiring between apparatuses.
For example, an apparatus which includes a receiving unit such as a TV tuner and a storing unit such as a hard disk can be installed in a home as a server apparatus. Then, contents such as a movie held in the server apparatus is transmitted to a client apparatus such as a digital TV and a PC via a home network. With this, the client apparatus can reproduce the contents while receiving data, and thus so-called content data stream distribution and reproduction processing is performed.
In the case of content data stream distribution between the server apparatus and the client apparatus that are connected through wireless connection, lack of communication bandwidth occurs due to characteristics of the wireless communication, when a distance between devices is long or depending on the environment where the device is installed. Consequently, a problem such as delay in streaming data distribution occurs.
To address this problem, for example, Patent Literature (PTL) 1 proposes a method for judging whether or not a wireless section exists between the server apparatus and the client apparatus, and transmitting data efficiently adapted for the wireless section.
FIG. 6 is a functional block diagram showing a transmitting apparatus included in a communication control apparatus according to a conventional example of the present invention. The transmitting apparatus shown in FIG. 6 calculates bandwidth using two packets having mutually different length. Specifically, the transmitting apparatus includes: a network bandwidth calculation unit 401 which calculates a network bandwidth by dividing a total amount of data, which is received by a receiving side, by the time taken for the reception; and a wireless section estimation unit 402 which estimates whether or not a wireless section as a wireless transmission path exists in a network through which data is to be transmitted, by comparing a network bandwidth at the time of a first packet size and a network bandwidth at the time of a second packet size that have been calculated by the network bandwidth calculation unit 401.
That is, in the case of a wireless LAN compliant with IEEE 802.11, a transmission waiting time and an ACK for delivery confirmation are added to each of data packets to be transmitted. Accordingly, for example, when it is assumed that 1500-byte data is transmitted, there is a large difference in throughout when five packets each containing a 300-byte are transmitted, compared to a case where one packet containing a 1500-byte is transmitted. This is because the transmission waiting time takes five times as long and waiting time for ACK response takes five times as long. Due to this, when the difference in the network bandwidths calculated using the packets of two different sizes is equal to or larger than a predetermined threshold value, it is possible to judge that there is a wireless section.
When a wired LAN is used, the transmission waiting time is significantly short compared to the transmission waiting time of the wireless LAN. Also, there is no ACK response for delivery confirmation. Thus, when the difference in packet size is as much as about the difference between the 300-byte and the 1500-byte, a large difference in a communication time that is observed when the wireless LAN is used is not observed. In other words, a decrease in transmission throughput does not occur. Thus, taking advantage of the above described characteristics, it is possible to estimate that there is a wireless section in a certain section of a network through which data is to be transmitted, when a difference between the network bandwidth measured with the packet containing 1500-byte and a network bandwidth measured with the packets each containing 300-byte is, for example, 50% or more of the network bandwidth measured with a packet containing 1500-byte.
Estimation of the wireless section as described above allows efficient data transmission adapted for wireless sections. For example, data to be transmitted is coded such that the data has error tolerance, or, a plurality of frame data to be transmitted is packetized into one packet.